Multitrack tape device using a movable magnetic head with a planar surface and including a tape supporting device

ABSTRACT

A tape recorder and/or a playback device for a multitrack tape utilizes a magnetic head having active parts for recording and/or reading microtracks with the active parts being arranged in a two-dimensional matrix within a substantially planar surface of the magnetic head. A pressure device assures contact between the microtracks and the active parts by acting on a backside surface of the tape opposite to the front side surface containing the magnetic head. A structure allows for positioning the magnetic head in front of either one of at least two macrotracks which bundle addressed microtracks. A portion of the tape surface is supported adjacent to the macrotrack bundling the addressed microtracks to prevent unwanted tape deformation.

BACKGROUND OF THE INVENTION

The invention relates to a tape recorder and/or playback device forrecording and/or reading on a multitrack tape.

In devices of the above mentioned type it is known to use a magnetichead to write and/or read tracks on a multitrack magnetic tape. A trackis called a macrotrack when it bundles a plurality of smaller elementarymicrotracks. A magnetic head may comprise a plurality of active parts,each part being used to write and/or read in one microtrack at the timeand the number of active parts being large enough to write in all themicrotracks of a macrotrack simultaneously. An example for a device ofthe above mentioned type is a SDVCR (Stationary Digital Video CassetteRecorder) in which a stationary magnetic head is used to address all themicrotracks over the whole width of the tape simultaneously (Reference1: High-Data-Rate, High-Density Magnetic Tape Recorder Using MatrixWriting Head and Kerr Reading Head, J. C. Lehureau and J-P. Castera,THOMSON-CSF Central research Lab, Orsay, Proceedings of the 13th IEEESymposium on Mass Storage Systems, Annecy, France, Jun. 12-16, 1994,pp127-130). The active parts of a SDVCR magnetic head are usuallyarranged in a two-dimensional matrix within a surface of the magnetichead. The surface containing the matrix of active parts is typicallyobtained by polishing a multi-layer structure until the active parts andtheir magnetic gaps appear on the surface. Surfaces obtained by thismethod are substantially planar, therefore a problem occurs when onetries to bring in contact all the active parts of the matrix with theircorresponding microtracks at the tape surface. The tape which is verythin by nature will tend to loose contact above the relatively large andplanar surface containing the matrix of active parts of the magnetichead. To assure the contact between the microtracks and the active partsan airflow system flattens the tape against the planar surface(Reference 2: Head to Tape Contact Characterization for a 384 TracksFixed Magnetic Head, F. Le Texier, N. Blanchard, J-M. Coutellier,THOMSON-CSF, Electrochemical Society Fall Meeting 91, Phoenix, U.S.A.).

The SDVCR magnetic head is typically designed to address a relativelylarge number of microtracks simultaneously, e.g. 1024 tracks. Thecomplex technology used to produce the SDVCR magnetic head may causerelatively high production costs. In addition the volume needed toincorporate an airflow system turns out to have drawbacks, speciallywhen integrating it in a compact and perhaps portable SDVCR.

SUMMARY OF THE INVENTION

The first problem solved by the present invention is to find a solutionfor a device of the above mentioned type in which a cheaper magnetichead can be used to write and/or read the microtracks. Additionally acompact and more simple solution for means to assure an intimate contacteverywhere between the microtracks and the active parts of the magnetichead is suggested.

The above raised problem is solved by the present invention whichconsists of a magnetic tape recorder and/or playback device forrecording and/or reading on a magnetic tape having a magnetic layer at afront side surface on which a plurality of information microtracks whichare parallel to a direction of transportation of the tape may berecorded, said device comprising at least a magnetic head having activeparts for recording and/or reading microtracks, the active parts beingarranged in a two-dimensional matrix within a substantially planarsurface of the magnetic head in a way that a microtrack is addressedrespectively by one dedicated active part of said matrix, means fortransporting the tape in front of the active parts of the magnetic head,and pressure means assuring contact between the microtracks and saidactive parts by acting on a back side surface of the tape opposite tothe front side surface of the tape, in which said device comprises meansfor moving the magnetic head in a direction secant to the direction ofthe microtracks in order to position said active parts in front ofaddressed microtracks bundled in either one of at least two macrotracks,and means for supporting a portion of the tape surface carryingmacrotracks which are adjacent to the macrotrack bundling said addressedmicrotracks to prevent unwanted tape deformation, said means forsupporting being distinct from the magnetic head. The device accordingto the present invention may use a magnetic head with fewer active partsthan the magnetic head known from the prior art. For this reason thedevice according to the invention may also be cheaper to produce. Thedevice according to the invention can be used to write and/or read anumber of microtracks which is greater than the number of active partscontained on the magnetic head surface. This is achieved by moving themagnetic head in a direction secant to the direction of the microtracks,thus moving the active parts from one macrotrack to another one. Alimited number of microtracks that can be addressed simultaneously usingthe active parts on the magnetic head surface are bundled in amacrotrack. Hence the number of active parts on the magnetic head can beused to define the number of macrotracks that will bundle themicrotracks. The magnetic tape will carry at least 2 macrotracks acrossits width. The width of the magnetic head measured along a tapewidthdirection is at least as large as the width of a macrotrack. Duringwriting and/or reading in a macrotrack, the tape is pressed on thesurface of the magnetic head using the pressure means. In some cases,this may lead to an irreversible tape deformation (deterioration)occurring at edges of the magnetic head. To prevent this deformation,the device according to the invention uses means for supporting theportion of the tape which is adjacent to and goes over the planarsurface of the magnetic head containing the active parts.

In a further embodiment of the device according to the invention, thepressure means are mounted on a movable support which allows thepressure means to be disengaged from the tape, the pressure meansthereby releasing pressure on the back side surface of the tape. Thedevice according to the further embodiment has the advantage that themagnetic head may be moved more quickly in a direction secant to thedirection of the macrotracks when the pressure means are disengaged fromthe tape. The risks of tearing or damaging the tape are greatlydiminished this way.

In another embodiment of the device according to the invention, themeans for supporting and the pressure means are the same means. Thisembodiment leads to a further simplification of the device and reductionof the production costs.

The device according to the invention may also have the means forsupporting located on the front side surface of the tape. In thisembodiment the means for supporting is mounted around the magnetic headand have the same movement as the magnetic head when the magnetic headis displaced in a direction secant to the direction of the microtracks.This embodiment of the device according to the invention allows themagnetic head to be moved relatively quickly without having to disengagethe support means from the tape.

In an other preferred embodiment of the device according to theinvention, the means for supporting comprises a plate which is locatedon the front side surface of the tape. This plate has a slanting openingin a direction secant to the direction of the macrotracks in which themagnetic head can slide to address different macrotracks. The pressuremeans is mounted on a support which allows it to be displaced in a wayto assure said contact between the macrotracks and the active parts whenthe magnetic head is moved. In this embodiment, the magnetic head can bemoved relatively quickly while the means for supporting does not havethe same movement as the magnetic head but stays fixed. Furthermore,this embodiment is very compact and may be used to realize a compact andportable device according to the invention.

In a still further preferred embodiment of the device according to theinvention, the pressure means comprises a pressure pad which is made ofan elastic medium and a surface of which is used to press on the backside surface of the tape. This is a simple way to achieve the pressuremeans. In a more sophisticated embodiment of the device according to theinvention, the pressure means comprises a pressure roller which is madeof an elastic medium and is mounted on an axis perpendicular to thedirection of the microtracks, a surface of the pressure roller beingused to press on the back side surface of the tape. This way thefriction on the back side surface of the tape is reduced.

In an advantageous embodiment of the device according to the inventionthe active parts of the magnetic head are used for writing and themicrotracks are read using an optical system associated to said magnetichead and comprising at least a polarized light source, a magneto-opticaltransducer and a linear optical sensor. This advantageous embodimentallows to write relatively narrow microtracks which may be read usingthe optical system at a very low tape transportation speed. Additionallya relatively high density of information on the tape is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will appear fromthe following description of several examples, made with reference tothe appended FIG. 1 to 9.

FIG. 1 contains a schematic representation of a portion of multitracktape and a schematic view on a surface of a magnetic head containing amatrix of active parts.

FIG. 2 schematically shows a part of a tape recorder and/or playbackdevice comprising a magnetic head, a pressure means, and tape beingwritten or read on.

FIG. 3 contains a schematic representation of a portion of tape carryingmacrotracks and a schematic view of a magnetic head surface containingactive parts.

FIG. 4 shows a schematic representation of a movable magnetic head usedto write and/or read macrotracks on tape.

FIG. 5 gives a schematic overview of a device according to theinvention.

FIG. 6 contains a schematic representation of a magnetic head addressinga track on tape and around which are located means for supporting.

FIG. 7 contains a schematic representation of the same device as in FIG.6 but with the magnetic head in a different position.

FIG. 8 shows a schematic view of a device using a plate as means forsupporting.

FIG. 9 shows a schematic sectional view through the line AA of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The examples and figures are given by way of illustration only, and thusare not limitative of the present invention. First a brief descriptionwill be given of a SDVCR type tape recorder device which is found inprior art as from reference 1. The portion of tape 1 shown in FIG. 1carries on its front side surface a plurality of microtracks 2 in adirection parallel to a direction 3 of transportation of the tape 1. Amagnetic head 5 used to write the microtracks 2 can also be seen inFIG. 1. A planar surface 6 of the magnetic head 5 comprises a pluralityof active parts 7. Each active part 7 is used to address one microtrack2. The active parts 7 are arranged in a two-dimensional matrix 8 whichis represented by dotted lines for reasons of comprehension. To amicrotrack 2 corresponds respectively one dedicated active part 7 inmatrix 8. In FIG. 2, a part of a tape recorder and/or playback device 9comprising the magnetic head 5, a pressure means 10 and a portion oftape 1 between them can be seen. The device 9 is represented in dottedlines and also comprises a means for transporting the tape, the reels onwhich the tape is wound and all the known mechanical and electronicdevices (all not shown) needed to realize a tape recorder and/orplayback device. The tape 1 is being transported in front the activeparts 7 of the magnetic head 5 while pressure means 10 assure thecontact between the microtracks 2 and the active parts 7. In the SDVCRthe pressure means 10 typically comprises an airflow system (not shown)to create the pressure on a back side surface of the tape.

For use in a device according to the invention, microtracks 2 may bebundled in at least two macrotracks 12 arranged on the tape 11 as shownin FIG. 3. Also shown in FIG. 3 is a simplified representation of amagnetic head 13 having a planar surface 14. The planar surface 14comprises active parts 7 which are arranged in a matrix. The number ofactive parts 7 contained on the planar surface 14 of magnetic head 13 istypically smaller than the number of active parts used in magnetic head5 of a SDVCR device as illustrated in FIG. 1 and 2. This rendersmagnetic head 13 cheaper to produce. The magnetic head 13 allows to readall the microtracks 2 of one macrotrack 12 at the time. As shown in FIG.4, the magnetic head 13 may be positioned in front of either macrotrack12 using means for moving 15. The means for moving 15 is part of thedevice 9 represented schematically using dotted lines. A pressure means16 in the form of a pressure pad (or a pressure roller) made of anelastic medium is used to assure the contact between the microtracks 2on tape 11 and the active parts 7 of the magnetic head 13. The pressuremeans 16 at the same time prevents the tape from bending or folding (andthus deteriorating) around edges 17 of the magnetic head 13. Said edges17 delimit a zone of contact between the active parts 7 of the magnetichead 13 and the tape 11. Thus the pressure means 16 is also used as ameans for supporting a portion of the tape. In this embodiment the meansfor supporting 16 which is also pressure means is located on a back sidesurface of the tape 11 opposite to a front side surface of the tapealong which the magnetic head 13 is contacting. The portion of the tapeto be supported is adjacent to a tape area containing the contactsbetween the active parts of magnetic head 13 and the microtracks theyaddress. The means for supporting 16 is also part of the device 9.

FIG. 5 contains a schematic overall view of a device according to theinvention. In the shown embodiment, the tape 11 is wound on andtransported between two tape reels 18. The tape reels 18 may be used inconjunction with flanges and be driven using a clutch gear not shown.The tape transportation is achieved by rollers 19 and capstans 20. Tapeguides 21 are used to keep the tape 11 on a precise path. The pressuremeans 16 may also be used as means for supporting, e.g. when pressuremeans are large enough to support the total tape width. The pressuremeans 16 are mounted on a movable support 22 which allows the pressuremeans 16 to be disengaged from the tape as in a position shown in theFIG. 5. The magnetic head 13 is fixed part of a larger Head Optical Unit(HOU) 23 which also comprises optical means for an optical read-out ofthe microtracks as known from the prior art (see reference 1). Theoptical means comprises at least a polarized light source, a Kerr headand a CCD sensor. The magnetic head 13 is moved in the same way as theHOU 23. The HOU 23 slides along bearings 24 the orientation of which isperpendicular to the direction of the microtracks and parallel to thetape surface. The means for moving 15 the HOU 23 comprise a motor 25which drives a mechanical transmission 26 of a motor rotation to amovement of the HOU 23 along bearings 24.

In an embodiment shown in FIG. 6, means for supporting 27 the tape 11are mounted around the magnetic head 13. The means for supporting 27 aremoved at the same time as the magnetic head 13 by the means for moving15. A pressure means 28 presses on the back side surface of tape 11. Thepressure means 28 can be moved by means 29 which are very similar tomeans for moving 15. The means for supporting 27 supports a portion ofthe tape surface which is adjacent to the magnetic head 13 but not incontact with the active parts of the magnetic head 13. FIG. 7 shows thesame embodiment as in FIG. 6 but where the magnetic head 13 ispositioned to read a different macrotrack as in FIG. 6. A tape heightposition measured relatively to device 9 stays unchanged in FIG. 6 and7. Merely the magnetic head 13, the means for supporting 27 and thepressure means 28 are moved.

In FIG. 8, a plate 30 located on the front side of the tape, i.e. theside a magnetic head 31 is on, supports the tape 11. The plate 30 has aslanting opening 32 in a direction secant to the direction of themacrotracks 12 and in which the magnetic head 31 slides to addressmicrotracks of a macrotrack 12 on the tape 11. A pressure means 33comprising a pressure roller made out of an elastic medium and an axisaround which the roller rotates during tape transportation is used onthe back side of the tape to assure the contact between microtracks andactive parts of the magnetic head 31. The solution of the embodimentpresented in FIG. 8 is more compact in a direction perpendicular to themicrotracks as compared to the embodiment shown in FIG. 6 and 7. FIG. 9shows a sectional view through the line AA of the device shown in FIG.8. The pressure roller of pressure means 33 is shown in its compressedstate, the initial uncompressed state of the roller being shown by adotted line 34. The magnetic head 31 is slid by means for moving 35 inthe slanting opening 32, the pressure roller of pressure means 33 isdisplaced by displacing means 36 in the direction parallel to thedirection of the macrotracks so that said contact is assured at eachposition the magnetic head 31 may be set at.

We claim:
 1. A tape recorder and/or playback device for recording and/orreading on a magnetic tape having a magnetic layer at a front sidesurface on which a plurality of information microtracks which areparallel to a direction of transportation of the tape may be recorded,said device comprisingat least a magnetic head having active parts forrecording and/or reading microtracks, the active parts being arranged ina two-dimensional matrix within a substantially planar surface of themagnetic head in a way that a microtrack is addressed respectively byone dedicated active part of said matrix, means for transporting thetape in front of the active parts of the magnetic head and pressuremeans assuring contact between the microtracks and said active parts byacting on a back side surface of the tape opposite to the front sidesurface of the tape, characterized in that said device comprises meansfor moving the magnetic head in a direction secant to the direction ofthe microtracks in order to position said active parts in front ofaddressed microtracks bundled in one of at least two macrotracks and,means for supporting a portion of the tape surface carrying one or moremacrotracks which are adjacent to the macrotrack bundling said addressedmicrotracks to prevent unwanted tape deformation, said means forsupporting being distinct from the magnetic head.
 2. A tape recorderand/or playback device according to claim 1 characterized in that saidpressure means are mounted on a movable support which allows saidpressure means to be disengaged from the tape, said pressure meansthereby releasing pressure on the back side surface of the tape.
 3. Atape recorder and/or playback device according to claim 2 characterizedin that said means for supporting and said pressure means are the samemeans.
 4. A tape recorder and/or a playback device according to claim 2characterized in that said means for supporting is located on the frontside surface of the tape, is mounted around the magnetic head and hasthe same movement as the magnetic head when the magnetic head isdisplaced in said direction secant to the direction of the microtracks.5. A tape recorder and/or playback device according to claim 2characterized in that said means for supporting comprise a plate whichis located on the front side surface of the tape, said plate having aslanting opening in a direction secant to the direction of themicrotracks in which the magnetic head can slide to address differentmacrotracks, said pressure means being mounted on a displacing meanswhich allows said pressure means to be displaced in a way to assure saidcontact between the microtracks and the active parts when the magnetichead is moved.
 6. A tape recorder and/or playback device according toclaim 2, characterized in that said pressure means comprises a pressurepad which is made of an elastic medium and a surface of which is used topress on said back side surface of the tape.
 7. A tape recorder and/orplayback device according to claim 2, characterized in that saidpressure means comprises a pressure roller which is made of an elasticmedium and is mounted on an axis perpendicular to the direction of themicrotracks, a surface of the pressure roller being used to press on theback side surface of the tape.
 8. A tape recorder and/or playback deviceaccording to claim 2, characterized in that said active parts of themagnetic head are used for writing only and that the microtracks areread using an optical system associated to said magnetic head andcomprising at least a polarized light source, a magneto-opticaltransducer and a linear optical sensor.
 9. A tape recorder and/orplayback device according to claim 1 characterized in that said meansfor supporting and said pressure means are the same means.
 10. A taperecorder and/or playback device according to claim 9, characterized inthat said pressure means comprises a pressure pad which is made of anelastic medium and a surface of which is used to press on said back sidesurface of the tape.
 11. A tape recorder and/or playback deviceaccording to claim 9, characterized in that said pressure meanscomprises a pressure roller which is made of an elastic medium and ismounted on an axis perpendicular to the direction of the microtracks, asurface of the pressure roller being used to press on the back sidesurface of the tape.
 12. A tape recorder and/or a playback deviceaccording to claim 1 characterized in that said means for supporting islocated on the front side surface of the tape, is mounted around themagnetic head and has the same movement as the magnetic head when themagnetic head is displaced in said direction secant to the direction ofthe microtracks.
 13. A tape recorder and/or playback device according toclaim 12, characterized in that said pressure means comprises a pressurepad which is made of an elastic medium and a surface of which is used topress on said back side surface of the tape.
 14. A tape recorder and/orplayback device according to claim 12, characterized in that saidpressure means comprises a pressure roller which is made of an elasticmedium and is mounted on an axis perpendicular to the direction of themicrotracks, a surface of the pressure roller being used to press on theback side surface of the tape.
 15. A tape recorder and/or playbackdevice according to claim 1 characterized in that said means forsupporting comprise a plate which is located on the front side surfaceof the tape, said plate having a slanting opening in a direction secantto the direction of the microtracks in which the magnetic head can slideto address different macrotracks, said pressure means being mounted on adisplacing means which allows said pressure means to be displaced in away to assure said contact between the microtracks and the active partswhen the magnetic head is moved.
 16. A tape recorder and/or playbackdevice according to claim 15, characterized in that said pressure meanscomprises a pressure pad which is made of an elastic medium and asurface of which is used to press on said back side surface of the tape.17. A tape recorder and/or playback device according to claim 15,characterized in that said pressure means comprises a pressure rollerwhich is made of an elastic medium and is mounted on an axisperpendicular to the direction of the microtracks, a surface of thepressure roller being used to press on the back side surface of thetape.
 18. A tape recorder and/or playback device according to claim 1characterized in that said pressure means comprises a pressure pad whichis made of an elastic medium and a surface of which is used to press onsaid back side surface of the tape.
 19. A tape recorder and/or playbackdevice according to claim 1 characterized in that said pressure meanscomprises a pressure roller which is made of an elastic medium and ismounted on an axis perpendicular to the direction of the microtracks, asurface of the pressure roller being used to press on the back sidesurface of the tape.
 20. A tape recorder and/or playback deviceaccording to claim 1 characterized in that said active parts of themagnetic head are used for writing only and that the microtracks areread using an optical system associated to said magnetic head andcomprising at least a polarized light source, a magneto-opticaltransducer and a linear optical sensor.